<!doctype html>
<html>
<head>
<meta charset="utf-8">
<title>无标题文档</title>

<style type="text/css">
div {
	width:350px;
	height:60px;
	background-color:#ddd;
	margin:5px;
}

div>.a {
	width:200px;
	height:35px;
	border:2px dotted black;
	background-color:#111;
}

div .a {
	width:200px;
	height:35px;
	border:2px dotted black;
	background-color:#999;
}

/*上面两个东西是平级的*/
	
</style>
</head>
<body>
<div>没有任何属性的div元素</div>
<div><p class="a">class属性为a且div的子节点的元素</p></div>
<div><section><p class="a">考察一下孙子元素</p></section></div>
</body>
</html>
